Common problem in the control and operation of rotary wing aircraft, such as helicopters, is in the control of the pitch of the rotor blades as the rotor rotate to provide lift and control to the helicopter. As is well known, the lift and control provided by the rotor blades is generally achieved by altering the pitch of the rotor blades as the blades rotate, which in turn results in rapidly changing dynamic loads on the blades during rotation, due in part to the dynamic forces induced due to the changing pitches of the blades and in part due to aerodynamic forces acting on the blades. These problems are compounded by dynamic forces, such as vibration, from the helicopter power and drive trains and aerodynamic forces acting on the body and other surfaces of the helicopter.
These problems, in turn, result in yet other problems, such as excessive noise generated by the rotors, increased power consumption, increased control loads on the helicopter control systems, including the pilot, and increased vibration and stresses on the entire rotor and power system and the components thereof and on the structural components of the aircraft.
The rotor control systems of the prior art have generally attempted to control the pitch of the rotor blades by direct means, starting with the pilot controls and extending through the actual rotor control mechanisms which, as is well known and for example, include a swash plate pitch horns for controlling the actual pitches of the blades. In general, however, the rotor control systems of the prior art have generates a single control signal of some form, that is, as an electronic or electrical signal or as a mechanical or hydraulic force, for the entire rotor system, and has phase shafted this control signal, by actuation of the swash plate, to actuate the pitch of the individual blades around the rotation path of the blades. This approach, however, does not address the sources of vibration and other unwanted physical effects resulting from the rotor blades as individual elements in dynamic motion around the rotation path.
Other approaches to the reduction of rotor noise and vibration have been directed to, for example, the physical structure and materials of the rotor blades and the blade actuation mechanisms. While advantageous in some respects, these approaches again do not address the effects of vibration and other unwanted physical effects resulting from the rotor blades as individual elements in dynamic motion around the rotation path. These methods instead essentially attempt to dissipate the vibration in the structure or materials of the blades and the drive train, which shifts the end result of the problem but which does not address the adverse results in terms of such matters as, for example, excessive wear of the rotor, drive train and structural components, fuel consumption and control system load. In fact, these approaches may worsen the problems in some respects by substituting a quieter rotor material for a more durable rotor material.
The present invention addresses these and related problems of the prior art.